1. Field of the Invention
This invention is directed to a printhead driver for a wire matrix printer and particularly to a switching regulator type driver for driving one or more solenoids simultaneously, the armatures of such solenoids driving the corresponding print needles.
2. Description of the Prior Art
Prior art wire matrix solenoid drivers have had power supplies that were large enough to provide power for a maximum of all of the solenoids being turned on at the same time to drive their armatures simultaneously. This type of driver required a relatively large amount of power to operate with attendant problems such as excessive weight and heat dissipation. State of the art solenoid drivers are of the switching regulator variety but utilize a power switch for each solenoid so that the number of power switches equals the number of solenoids. This type of driver requires much less power but has the disadvantage of a relatively large amount of circuitry.
Not only does this invention provide a greatly reduced power requirement, but also greatly reduces the number of components by using a single power switch for all of the solenoids and by selecting values of inductance for the solenoids such that a quiesent current is reached or nearly reached at a predetermined time.